Submitted as: model evaluation paper 15 Oct 2021

Submitted as: model evaluation paper | 15 Oct 2021

Review status: this preprint is currently under review for the journal GMD.

IBI-CCS: a regional high-resolution model to evaluate western Europe sea level changes

Alisée A. Chaigneau1,2, Guillaume Reffray2, Aurore Voldoire1, and Angélique Melet2 Alisée A. Chaigneau et al.
  • 1CNRM UMR 3589, Météo-France/CNRS, Toulouse, France
  • 2Mercator Ocean International, Ramonville St Agne, France

Abstract. Projections of coastal sea level (SL) changes are of great interest for coastal risk assessment and decision-making. SL projections are typically produced using global climate models (GCMs) which cannot fully resolve SL changes at the coast due to their coarse resolution and lack of representation of some relevant processes. To overcome these limitations and refine projections at regional scales, GCMs can be dynamically downscaled through the implementation of a high-resolution regional climate model (RCM). In this study, we developed the IBI-CCS regional ocean model based on a 1/12 ° north-eastern Atlantic NEMO ocean model configuration to dynamically downscale CNRM-CM6-1-HR, a GCM with a ¼ ° resolution ocean model component developed for the Coupled Model Intercomparison Project 6th Phase (CMIP6) by the Centre National de Recherches Météorologiques (CNRM). For a more complete representation of processes driving coastal SL changes, tides and atmospheric surface pressure forcing are explicitly resolved in IBI-CCS in addition to the ocean general circulation. To limit the propagation of climate drifts and biases from the GCM into the regional simulations, several corrections are applied to the GCM fields used to force the RCM. The regional simulations are performed over the 1950 to 2100 period for two climate change scenarios (SSP1-2.6 and SSP5-8.5). To validate the dynamical downscaling method, the RCM and GCM simulations are compared to reanalyses and observations over the 1993–2014 period for a selection of ocean variables including SL. Results indicate that large-scale performances of IBI-CCS are better than those of the GCM thanks to the corrections applied to the RCM. Extreme SLs are also satisfactorily represented in the IBI-CCS historical simulation. Comparison of the RCM and GCM 21st century projections show a limited impact of increased resolution (1/4° to 1/12°) on SL changes. Overall, bias corrections have a moderate impact on projected coastal SL changes projections, except in the Mediterranean Sea where GCM biases were substantial.

Alisée A. Chaigneau et al.

Status: open (until 23 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2021-328', Anonymous Referee #1, 06 Nov 2021 reply
  • RC2: 'Comment on gmd-2021-328', Anonymous Referee #2, 03 Dec 2021 reply

Alisée A. Chaigneau et al.

Alisée A. Chaigneau et al.


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Short summary
Climate change induced sea level rise is a major threat for coastal and low-lying regions. Projections of coastal sea level changes are thus of great interest for coastal risk assessment and have significantly developed in recent years. In this paper, the objective is to provide high-resolution (6 km) projections of sea level changes in the north-eastern Atlantic region bordering western Europe. For that purpose, a regional model is used to refine existing coarse global projections.